1. Field of the Invention
The present invention relates to a signal transmission tube that has an inverse initiation retention seal that prevents the inverse propagation of an unintended shock wave and attenuates the creation of induced electrostatic charges.
2. Description of the Related Art
Several designs for detonator seals have been designed in the past. None of them, however, include an inverse retention seal built in the propagation tube itself that connects with a seal used with non-electric detonators to prevent unintended accidental detonation.
Detonators of the non-electric type are preferred in many applications, in particular mining, to avoid the inherent problems found with electric detonators such as rampant electrostatic charges induced by weather conditions or equipment nearby. The non-electric detonators typically take advantage of the high speed (1,500 meters per second) of the percussion gaseous waves to synchronized the detonation of various charges by interconnecting these non-electric detonators. Some detonators in the field are located on the surface, or otherwise in places susceptible to their accidental activation (a rock or tree branch falling on the detonator, a truck running over it, etc.). The accidental detonation is then transmitted to the other interconnected detonators creating a bigger problem. Thus, it is desirable to find a way to preventing the detonation of interconnected detonators when an accident causes one of the detonators to be activated. The present invention addresses this problem providing a simple novel solution that was not obvious before.
Fuse apparatuses that utilize transmission tubes have been disclosed in the past. In U.S. Pat. No. 3,590,739 issued to Persson in 1971 discloses the use of a shock tube or duct for propagating a gaseous percussion wave to activate non-electric detonators. There is no provision, however, for preventing the inverse initiation of signals as claimed herein or the suggestion of any seals.
Applicant believes that another related reference corresponds to PCT patent No. PCT/US2011/027639 filed by DYNO NOBEL INC. et al on Mar. 9, 2011 claiming international priority under U.S. Ser. No. 61/311,857 filed on Mar. 9, 2010. However, it differs from the present invention because the seal is not built in the shock tube, at a predetermined distance from its end. And there is no suggestion in the Dyno Nobel reference on preventing the propagation of the shock wave signal in the direction opposite to what the shock tube is designed for. Instead, the reference is concerned with maintaining the explosive pressures providing a gas impermeable seal and obviating the need for an ignition buffer. The seal in the present invention, on the other hand, prevents the propagation of the wave traveling from the detonator accidentally triggered to other detonators connected to the shock tube. There is no suggestion of modifying the shock tube, at a predetermined distance from its end, to prevent the wave from traveling back and initiating additional detonations.
Other documents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.